Lock and key theory of acetylcholine

Question

The question is

According to lock and key theory single molecule will fit into single receptor only. How does Acetylcholine will binds to both Nicotinic (ligand gated receptor) and muscarinic receptor (g protein receptor)?

If so, is that lock and key theory is wrong?

Answer 1

I think your understanding of the lock and key theory may be too literal. The lock and key theory suggests that an enzyme-substrate interaction can only happen if they possess complementary shapes (or electrovalence). This being the case, a neurotransmitter can bind to more than one specific receptor if the receptor has a specifically complementary binding capacity. Just as there are several subtypes of dopamine receptors in the central and peripheral nervous systems resulting in a variety of outcomes, nicotinic and muscarinic receptors have different structure, electron valence and function depending on location and specific chemical bonds. Science is only beginning to understand the cannabinoid neurotransmitters and already have identified several types of receptors with which they may bind. The metaphor of lock and key is still appropriate as it is placing the potentially successful chemical bonds and their resulting outcomes into a context for generalized understanding.